Recently, a thinned and large-area silicone wafer has been developed. Such a thin silicone wafer is breakable, and when being stressed in handling, cracks or micro-cracks are generated so that performance of a silicone wafer is degraded to reduce the quality and defective products are increased.
In order to prevent the cracks or micro cracks on the silicone wafer from being generated, a wafer protective tape has been developed (for example, see Patent Document 1).
The wafer protective tape 800 is, as shown in FIG. 6, constituted by applying an adhesive or a bonding adhesive 802 on one surface of a tape-like supporter 803. A tape-like supporter is attached on the silicone wafer via the adhesive 802 and a silicone wafer 101 is protected by the tape-like supporter from a back side. When the protection is unnecessary, the wafer protection tape 800 is released by use of a protection tape releasing apparatus, or the like and then scrapped.
By use of such a wafer protection tape 800, even if the silicon wafer 101 to be thinly polished is used, it is reinforced during transferring between processes or processing, so that the generation of cracks is suppressed.
On the other hand, conventionally, an electrostatic holding apparatus has been known as a holding apparatus being configured to hold a thin-film material such as a silicone wafer (see, for example, Patent documents 2, 3).
In such an electrostatic holding apparatus, a holding part is attached to a base plate, the holding part having a voltage controller being mainly constituted by an electrode element group configured to provide a pair of positive-negative charges and an insulating layer configured to cover and fix the electrode element group on the base plate and being configured to apply high voltage to the electrode element group and to discharge the applied voltage.
Thereby, by applying high voltage via the switches disposed on the voltage controller of these electrode element groups, a handling object is held by an electrostatic attraction force induced between the silicone wafer as the handling object and a surface of the insulating layer as a holding surface. When the switch is turned off, these electrostatic attraction forces are canceled and the handling object can be released. Thereby, the handling object such as a conductor, a semiconductor or a high resistive element is attracted by the electrostatic attraction force and held (loaded) and when being released, it functions as an electrostatic chuck configured to attach and detach (unloaded) the handling object.    [Patent Document 1] Japanese Patent Application Publication No. 2001-319906    [Patent Document 2] Japanese Patent Application Publication No. 2003-282671    [Patent Document 3] Japanese Patent Application Publication No. 2004-358562    [Patent Document 4] Japanese Patent Application Publication No. 2006-52075